PFGE Protocols to Distinguish Subspecies of Lactococcus lactis

Pulsed-fi eld gel electrophoresis (PFGE), developed in the mid-1980s, rapidly became a “gold standard” method for analyzing bacterial chromosomes. Today, although outcompeted in resolution by alternative methods, such as optical mapping, and not applicable for high-throughput analyses, PFGE remains a valuable method for bacterial strain typing. Here, we describe optimized protocols for macrorestriction fi ngerprinting, characterization of plasmid complements, and gene localization by DNA-DNA hybridization of Lactococcus lactis genomes.